The present invention relates to apparatus for manipulating deformable sheet-like blanks which consist of paper, metallic foil, plastic foil or other suitable wrapping material. More particularly, the invention relates to improvements in apparatus for converting sheet-like blanks into tubular envelopes by draping the blanks around patterns whose configuration corresponds to that of packs for cigarettes, cigars, cigarillos or other rod-like smokers' products.
A packing machine for groups of cigarettes or the like normally comprises at least one turret which is driven continuously and carries a number of equidistant prismatic mandrels which advance first along a blank-applying station and thereupon past several blank-folding or draping stations where the blanks are converted into tubular envelopes each of which surrounds four sides of the respective mandrel. Each tubular envelope is thereupon closed at one end so that a group of cigarettes can be introduced into its interior through the other end which remains open. The other end of each envelope is thereupon closed, for example, by a revenue label. If the packs consist of several layers, each mandrel receives several blanks each of which is converted into a layer of the finished pack. Reference may be had to the commonly owned U.S. Pat. No. 3,750,676 granted Aug. 7, 1973 to Kruse et al.; this patent discloses a machine for the making of ciagarette packs each of which consists of an inner layer of metallic foil and an outer layer of paper or cardboard.
When the turret which carries the mandrels is driven uninterruptedly, i.e., without periods of dwell, the draping of blanks around the mandrels is performed by a host of instrumentalities including at least one folding member for each mandrel. Such folding members travel with the respective mandrels along a circular path and are caused to perform predetermined movements with respect to the associated mandrels to thereby carry out certain folding operations upon the blanks. As a rule, the folding members are caused to move relative to the mandrels by stationary cams or ways which are adjacent to the path of movement of the mandrels. The machine further comprises means for pressing the blanks against the respective mandrels so as to prevent undesirable shifting of blanks during conversion into tubular envelopes and thereupon into finished layers of cigarette packs.
A drawback of the just described packing machines is that the mechanism for converting blanks into tubular envelopes is complex, expensive and prone to malfunction. This is attributable to a large extent to the fact that such mechanism must include at least one discrete folding member for each mandrel. Repeated impacting of mobile folding members against cams or ways results in pronounced wear and creates considerable noise. Moreover, the means for pressing the blanks against the adjacent mandrels is likely to permit at least some shifting of blanks, especially if the turret is rotated at a high speed which is desirable in modern packing machines. Improper folding of a single blank or of a short series of blanks necessitates a lengthy interruption in the operation of the packing machine with attendant losses in output, especially if the packing machine forms part of a production line which further includes one or more cigarette rod making machines and one or more filter cigarette making machines.